Boeing B-47E Stratojet

Last revised June 7, 2008



The B-47E (Model 450-157-35) was the major production version of the Stratojet. It was the only version that was mass-produced by all three members of the Stratojet production pool--a total of 1341 B-47Es were built--386 by Lockheed, 264 by Douglas, and 691 by Boeing.

The B-47E was basically the standardized production version of the Stratojet, and incorporated many innovations that had been suggested by experience with the B-47B. It standardized on six General Electric J47-GE-25 engines, which offered a thrust of 7200 pounds with water injection. These engines had already been refitted to several B-47Bs. The 18-unit internal JATO system was retained on early models, but was soon replaced by a jettisonable rack that contained 33 1000 lb.s.t units that could be dropped following takeoff. The B-47E was fitted from the start with an approach chute to increase drag and a brake chute to decrease the landing roll. An anti-skid braking device was also fitted.

The defensive armament was changed to two 20-mm cannon in the tail. The A-5 fire control system that had taken so long to develop was finally fitted. The A-5 fire control system was much better than the discarded B-4 system of earlier versions, and could automatically detect and track pursuing aircraft and aim and fire the 20-mm cannon. The earlier B-4 system could at best spray machine gun fire in the general direction of an attacking plane, without much prospect of actually scoring a hit.

The B-47E incorporated as standard equipment an inflight refuelling receptacle for flying-boom midair refuelling on the starboard side of the nose. The use of inflight-refuelling capability enabled the total fuel capacity to be reduced to 14,610 gallons, including two 1700-gallon drop tanks carried underneath the wings between the engine nacelles. 

The crew was finally provided with ejector seats as standard equipment, with the pilot and copilot ejecting upward over the tail and the bombardier/navigator ejecting downward through a hatch in the lower nose.

The undersurfaces and lower portion of the fuselage of most B-47Es were painted a glossy white to reflect the heat radiation from nuclear blasts. This reflective paint was applied retroactively to some B-47Bs.

During FY 1953 production, a clamshell cockpit canopy was introduced, hinged on the right side.

The first B-47E flew on January 30, 1953, and the Air Force accepted this plane in February. By mid-year, 127 similar production examples had been delivered. The first B-47Es went in April 1953 to the 303rd Medium Bomb Wing based at Davis Monthan AFB in Arizona. The next recipient of the B-47E was the 22nd Wing at March AFB in California, retiring their B-47Bs to the Air Training Command.

By mid 1953, peak B-47 procurement was expected to reach almost 2200, but was cut by 140 in September 1953. A further production cut of 200 aircraft considered in October was prevented in favor of a 20-month production stretchout during the period in which the B-52 production line was getting up to speed. In contrast to the B-36 program, which was on the verge of cancellation several times, there was never any significant effort to cancel the B-47 program.

The B-47E rapidly became the dominant component of the USAF strategic deterrent during the mid- and late-1950s. By December of 1953, SAC had 8 B-47 Medium Bomber Wings. In December 1954, the SAC inventory counted 17 fully-equipped B-47 wings. By the beginning of 1956, 22 medium bombing wings had received the B-47, and another 5 wings were getting ready to convert to the B-47. In December 1956, SAC had 27 combat-ready B-47 wings, with 1204 combat-ready B-47 crews and 1306 B-47 aircraft assigned.

Progressive modifications resulted in four sub-variants of the B-47E.

The first of these, designated B-47E-I, introduced water/alcohol-injected J-47-GE-25A engines, rated at 7200 lb/st each. Phase II ECM equipment was provided, denoted by a small circular antenna on the rear fuselage. Maximum takeoff weight was 200,000 pounds.

A modified landing gear allowing heavier takeoff weights appeared on the 521st and subsequent B-47Es, and this configuration was labeled B-47E-II. Other modifications included the addition of Phase III ECM gear, which consisted of an AN-ALT-6 jammer mounted in a bulged fairing underneath the rear fuselage and antennae housed in wingtip extensions. The first B-47E-II reached the Air Force in August of 1953.

The B-47E-III introduced a three-phase electrical power supply

A far stronger landing gear was incorporated on the 862nd and later B-47E. This configuration was known as B-47E-IV. The IV also introduced a series of electronics upgrades including the MA-7A bombing radar, the AN/ASP-54 warning radar, and the AN/APG-39 gun-laying radar. The B-47E-IV had a takeoff weight of 230,000 pounds, 28,000 pounds more than previously permissible. This extra weight was largely devoted to extra fuel, enabling the combat radius of the IV to increase to 2050 nautical miles, almost twice the distance demonstrated 5 years earlier by the first B-47A. The maximum warload was 25,000 pounds.

The Air Force received its first B-47E-IV in February 1955. In March of 1955, it was decided that all active B-47s would be brought up to the IV standard.

Spurred by the Suez crisis of 1956, SAC demonstrated its ability to launch a large striking force on short notice when in December more than 1000 B-47s flew nonstop, simulated combat missions, averaging 8000 miles each over the American continent and Arctic regions.

Early in 1955, the Strategic Air Command requested the B-47 be adapted for low-level bombing, with the aircraft delivering its bomb via the toss-bomb technique. In a toss-bombing attack, the plane enters the run at low altitude, pulls up sharply into a half loop with a half roll on top and releases the bomb at a predetermined point in the climb. The bomb continues upward in a high arc, falling on the target at a considerable distance from its release point. In the meantime, the maneuver allows the airplane to reverse its direction and gives it more time to speed away to a safe distance from the blast. This technique was adopted because it was thought that high-speed B-47s flying at low level would be less vulnerable to enemy countermeasures. The existence of low-level capable B-47s would mean that a potential enemy would now be faced with threats from both high- and low-level attacks.

In June of 1955, a 6000-pound dummy bomb was successfully released from a B-47E during a 2.6g pullup from level flight. In another test flight, an 8850-pound practice bomb was dropped from a 2.5-g pullup. Despite some doubts about the structural integrity of the B-47 under the stresses involved in such maneuvers, in December 1955 SAC ordered that 125 B-47s be modified for low-level flight.

Low-level bombing involved special crew training. A training program known as Hairclipper was started in December of 1955. However, adverse weather, excessive maintenance requirements, serious deficiencies in LABS systems, and several accidents caused Hairclipper to be officially discontinued in March of 1958. However, the end of Hairclipper did not signify the end of low-level flying. A program known as Pop Up, a related training program that took advantage of recent advances in weapons developments, fared better. In the Pop Up maneuver, the aircraft came it low level, pulled up to high altitude, released its weapon, and then dove steeply to escape being spotted by enemy radars. Following the discovery of fatigue cracks in the wings of some B-47s in April of 1958, Pop Up was interrupted while the entire B-47 fleet could be checked. It was resumed in September, and by the end of 1959 the training program had finally been completed.

On January 25, 1957, a B-47 flew from March AFB, California to Hanscom Field, Massachusetts in 3 hours, 47 minutes, at an average speed of 710 mph (assisted by strong tailwinds). On August 14, 1957, a 321st Bomb Wing B-47 made a record nonstop flight from Andersen AFB, Guam to Sidi Slimane Air Base in French Morocco, a distance of 11,450 miles in 22 hours and 50 minutes. This required 4 midair refuellings. In November of 1959, a B-47 assigned to the Wright Air Development Center stayed in the air for 3 days 8 hours 36 minutes, covering 39,000 miles. This broke previous time-and-distance records.

The discovery of fatigue cracks in the wings of the B-47 during April of 1958 and a rash of new accidents in early 1958 triggered an immense inspection and repair program known as Milk Bottle. All three B-47 manufacturers as well as the AMC were involved in Milk Bottle. The low-level B-47s of the 306th and 22nd Bomb Wings were the first to enter the program, since they were most in danger of fatigue cracking. The program ended in July of 1959. Although Milk Bottle did not solve all the B-47's problems, it did go a long way in making operations with the B-47 a lot safer.

SAC initially wanted 1000 B-47s modified for low-level flying, which meant fitting virtually the entire Stratojet fleet with absolute altimeters, terrain-avoidance equipment, and Doppler radar. Because of the Milk Bottle repair program, testing delays, and the phaseout of some SAC B-47 wings due to a lack of funds, SAC was forced to scale down its low-altitude requirements to only 500 Stratojets. This program was given a new sense of urgency by the belief that by 1963 all B-47s would be hopelessly obsolete if they were not equipped for low-level flight. However, fund shortages dictated that SAC scale down its low-altitude requirements to only 350 aircraft.

A total of 691 B-47Es were built by Boeing-Wichita, Douglas-Tulsa built 264, and Lockheed-Marietta built 386. The final B-47E (53-6244) was delivered in 1957 to the 40th Bomb Wing, 44th Bomb Squadron at Schilling AFB in Salina, Kanses. 53-6244 was transfered to Lincoln AFB, Nebraska where it remained until it was transfered to the USAF Museum at Wright Patterson AFB, Ohio. Reports that 53-6244 served at Pease AFB are incorrect.

The beginning of the phaseout of the B-47E coincided with the delivery of the last example. In 1957, the 93rd Bomb Wing started exchanging its B-47s for B-52s. In March of 1961, President John F. Kennedy directed that the phaseout of the B-47 be accelerated. However this was delayed in July by the onset of the Berlin crisis of 1961-62. In the following years, B-47s were gradually delivered to the storage facility at Davis-Monthan AFB. SAC's last two B-47s went to storage on February 11, 1966.

Serials of Boeing B-47E Stratojet:

51-2357/2411 	Boeing B-47E-55-BW Stratojet			(55)
			Model 450-157-35, c/n 450410/450464
   			2358,2360,2362,2363,2366,2369,2373,2375,
			2380,2383,2385,2387,2390,2396,2397,2402,
			2406,2408 converted to WB-47E
			2360 on display at New England Air Museum
51-2412/2445 	Boeing B-47E-60-BW Stratojet			(34)
			Model 450-157-35, c/n 450465/450498
			2412/2415,1417,2420,2427,2435 converted to
			WB-47E
51-5214/5234	Boeing B-47E-60-BW Stratojet			(21)
			Model 450-157-35, c/n 450499/450519
			5219,5220 converted to YDB-47E for Rascal program
			5218,5257 converted to WB-47E
51-5235/5257	Boeing B-47E-65-BW Stratojet			(23)
			Model 450-157-35, c/n 450520/450542
51-7019/7050	Boeing B-47E-65-BW Stratojet			(32)
			Model 450-157-35, c/n 450562/450593
			7021,7046,7049 to WB-47E
51-7051/7064	Boeing B-47E-70-BW Stratojet			(14)
			Model 450-157-35, c/n 450594/450607
			7058, 7063 to WB-47E
51-7065/7083	Boeing B-47E-75-BW Stratojet			(19)
			Model 450-157-35, c/n 450608/450626
			7066 to WB-47E
51-15804/15810	Lockheed-Marietta B-47E-5-LM Stratojet		(7)
51-15811/15812	Lockheed-Marietta B-47E-10-LM Stratojet		(2)
51-17368/17386	Boeing B-47E-75-BW Stratojet			(19)
			Model 450-158-36, c/n 450660/450678
52-0019/0028	Douglas-Tulsa B-47E-1-DT Stratojet		(10)
			c/n 43637/43643
52-029/041	Douglas-Tulsa B-47E-5-DT Stratojet		(13)
			c/n 43644/43656
52-042/058	Douglas-Tulsa B-47E-10-DT Stratojet		(17)
			c/n 43657/43669, 43751/43754
52-059/081	Douglas-Tulsa B-47E-15-DT Stratojet		(23)
			c/n 43755/43777
52-082/111	Douglas-Tulsa B-47E-20-DT Stratojet		(30)
			c/n 43778/43807
52-112/120	Douglas-Tulsa B-47E-25-DT Stratojet		(9)
			c/n 43808/43816
52-146/176	Douglas-Tulsa B-47E-25-DT Stratojet		(31)
			c/n 44000/44030
			0166 on display at Castle AFB Museum
52-177/201	Douglas-Tulsa B-47E-30-DT Stratojet		(25)
			c/n 44031/44055
52-202/207	Lockheed-Marietta B-47E-10-LM Stratojet		(6)
52-208/220	Lockheed-Marietta B-47E-15-LM Stratojet		(13)
52-221/235	Lockheed-Marietta B-47E-20-LM Stratojet		(15)
52-236/260	Lockheed-Marietta B-47E-25-LM Stratojet		(25)
52-261/292	Lockheed-Marietta B-47E-30-LM Stratojet		(32)
52-293/330	Lockheed-Marietta B-47E-35-LM Stratojet		(38)
			0305 converted to EB-47L
52-331/362	Lockheed-Marietta B-47E-40-LM Stratojet		(32)
52-363/393	Lockheed-Marietta B-47E-45-LM Stratojet		(31)
			0389 to JB-47E
52-394/431	Boeing B-47E-80-BW Stratojet			(38)
			Model 450-157-35, c/n 450679/450716
52-432/469	Boeing B-47E-85-BW Stratojet			(38)
			Model 450-157-35, c/n 450717/450754
52-470/507	Boeing B-47E-90-BW Stratojet			(38)
			Model 450-157-35, c/n 450755/450792
52-508/545	Boeing B-47E-95-BW Stratojet			(38)
			Model 450-157-35, c/n 450793/450830
52-546/583	Boeing B-47E-100-BW Stratojet			(38)
			Model 450-157-35, c/n 450831/450868
52-584/620 	Boeing B-47E-105-BW Stratojet			(37)
			Model 450-157-35, c/n 450869/450905
52-621/684	Cancelled contract for B-47E Stratojet
52-1406/1417	Douglas-Tulsa B-47E-35-DT Stratojet		(12)
			c/n 44090/44101
52-3343/3373	Lockheed B-47E-50-LM Stratojet			(31)
53-1819/1849	Lockheed-Marietta B-47E-55-LM Stratojet		(31)
53-1850/1880	Lockheed-Marietta B-47E-60-LM Stratojet		(31)
53-1881/1911	Lockheed-Marietta B-47E-65-LM Stratojet		(31)
53-1912/1942	Lockheed-Marietta B-47E-70-LM Stratojet		(31)
53-1943/1972	Lockheed-Marietta B-47E-55-LM Stratojet		(30)
53-1973/2027	cancelled contract for B-47E
53-2028/2040	Douglas-Tulsa B-47E-35-DT Stratojet		(13)
			c/n 44149/44161
53-2041/2089	Douglas-Tulsa B-47E-DT Stratojet - all cancelled
53-2090/2103	Douglas-Tulsa B-47E-40-DT Stratojet		(14)
			c/n 44436/44449
53-2104/2117	Douglas-Tulsa B-47E-45-DT Stratojet		(14)
			c/n 44450/44463
53-2118/2131	Douglas-Tulsa B-47E-50-DT Stratojet		(14)
			c/n 44464/44477
53-2132/2144	Douglas-Tulsa B-47E-55-DT Stratojet		(13)
			c/n 44478/44490
53-2145/2157	Douglas-Tulsa B-47E-60-DT Stratojet		(13)
			c/n 44491/44503
53-2158/2170	Douglas-Tulsa B-47E-65-DT Stratojet		(13)
			c/n 44504/44516 
53-2171/2260	Boeing B-47E-BW	Stratojet - all cancelled
53-2261/2296	Boeing B-47E-110-BW Stratojet			(36) 
			Model 450-157-35, c/n  4501074/4501109
			2280 on display at WPAFB Museum
53-2297/2331	Boeing B-47E-115-BW Stratojet			(35)
			Model 450-157-35, c/n  4501110/4501144
53-2332/2367	Boeing B-47E-120-BW Stratojet			(36)
			Model 450-157-35, c/n  4501145/4501180
			2345,2346 to DB-47E
53-2368/2402	Boeing B-47E-125-BW Stratojet			(35)
			Model 450-157-35, c/n  4501181/4501215
53-2403/2417	Boeing B-47E-130-BW Stratojet			(15)
			Model 450-157-35, c/n  4501216/4501230
53-4207/4244	Boeing B-47E-130-BW Stratojet			(38)
			Model 450-157-35, c/n  4501231/4501268
			some converted to ETB-47E and EB-47L
53-6193/6244	Boeing B-47E-135-BW Stratojet			(52)
			Model 450-157-35, c/n  4501334/4501385
			some converted to ETB-47E and EB-47L

Specification of Boeing B-47E Stratojet:

Engines: Six General Electric J47-GE-25 turbojets, 5970 lb.s.t dry and 7200 lb.s.t. with water injection. Performance: Maximum speed 607 mph at 16,300 feet, 557 mph at 38,500 feet. Cruising speed 500 mph. Stalling speed 175 mph. Service ceiling 33,100 feet, combat ceiling 40,500 feet. Combat climb rate 4660 feet per minute (maximum power). Combat radius 2013 miles with 10,845 pound bombload . 4035 miles ferry range withy 16,318 gallon fuel load. Takeoff ground run 10,400 feet, 7350 feet with JATO. Dimensions: Wingspan 116 feet 0 inches, length 107 feet 0 inches, height 27 feet 11 inches, wing area 1428 square feet. Weights: 79,074 pounds empty, 133,030 pounds combat, 198,180 pounds gross, 230,000 pounds maximum takeoff. Armament: Two 20-mm M24A1 cannon in extreme tail. Maximum bombload 25,000 pounds.

Sources:


  1. American Combat Planes, Third Enlarged Edition, Ray Wagner, Doubleday, 1982.

  2. Post World War II Bombers, Marcelle Size Knaack, Office of Air Force History, 1988.

  3. The Boeing B-47, Peter Bowers, Aircraft in Profile, Doubleday, 1968.

  4. Boeing Aircraft Since 1916, Peter M. Bowers, Naval Institute Press, 1989.

  5. United States Military Aircraft Since 1909, Gordon Swanborough and Peter M. Bowers, Smithsonian, 1989.

  6. Boeing B-47 Stratojet--Variant Briefing. Bill Yenne, International Air Power Review, Vol 6, 2002.

  7. E-mail from H. C. East on service of 53-6244, the last B-47.